For the roasted salsa: Preheat the broiler.
Spread out the tomatillos, serranos, the onion half and the garlic on a baking sheet. Broil for 20 minutes, until beginning to char. Flip and broil on the reverse side until charred; remove each item as it chars, until all are done. (Keep a close eye¿you don't want the vegetables overcharred). Set aside to cool to room temperature.
In a food processor or blender, combine the roasted vegetables with the spinach, cilantro and lime juice. Puree until smooth, adding 2 tablespoons water as needed. Season with salt.
For the avocado crema: In a blender or food processor, combine the avocado, Greek yogurt, lime zest and juice, salt and cumin. Process until smooth. Add water as needed, 1 tablespoon at a time until the crema acquires the consistency of soft-serve ice cream.
For the crunchy slaw: In a medium bowl, combine the cabbage, carrots, scallions, snow peas and salt; toss to combine. Let sit for about 10 minutes so the salt begins to wilt the cabbage.
Meanwhile, in a small bowl, whisk together the olive oil, lime juice and cumin. Add the dressing to the salted vegetables; toss well. Add the cilantro and set aside.
For the faux refried beans: In a heavy-bottomed pot set over medium-high heat, cook the bacon until it begins to render its fat. Add the onions and sweat until translucent. Add the garlic and cook until fragrant. Add the black beans and the cumin, and lower the heat to medium-low. Cook until the garlic begins to soften and the beans begin to break apart, about 20 minutes. Transfer to a food processor and puree until smooth. Season with salt to taste.
For the burrito: Heat the olive oil in a 12-inch skillet over medium-high heat. When it starts to smoke slightly, add the sweet potatoes and cook without stirring until well browned, 6 to 7 minutes. Once browned, stir and continue to brown and crisp until cooked through, 4 minutes more. Sprinkle with the salt, cayenne and ancho, then remove from the pan and set aside.
Lower the heat to medium and add the crumbled chorizo to the skillet. Cook until browned and cooked through, 3 to 5 minutes.
Build the burrito: Lay a tortilla on a work surface. Fill the rectangular area just below the middle of the tortilla and about 1 1/2 inches from either side with 3 tablespoons of the refried beans, 1/3 cup of the sweet potatoes, one-quarter of the chorizo, 3 tablespoons of the salsa, 2 tablespoons of the avocado crema and about 1/3 cup of the slaw. Repeat.
Roll up burrito-style: For each tortilla, fold in the sides and then fold up the bottom end, being careful to pull the sides in. Tuck the bottom flap close to the filling and roll forward to close the burrito.
Heat a griddle and a cast-iron pan over medium-high heat. Add 1 ounce of the cheddar to the griddle in a strip. Lay a burrito seam-side down on top of the cheese. Weight the burrito with the hot cast-iron pan and cook until the tortilla browns and the cheese releases, 30 seconds to 1 minute. Flip the burrito over and brown on the other side. Remove from the heat. Repeat with the remaining cheese and burritos. Slice the burritos in half and serve.